Selective coating apparatus

Abstract

Apparatus and methods for selectively coating the surfaces of objects are disclosed. The apparatus comprises a plurality of megasonic transducers which generate acoustical pressure waves in the megasonic frequency range in an upward direction and cause droplets of coating material to be expelled from a supply of the liquid coating material which is disposed above the transducers. The droplets travel in a generally upward direction toward the surface of the object to be coated which is held in an inverted, i.e., downward position.

We claim: 
     
       1. Apparatus for selectively coating a surface of an object with a coating material comprising: a plurality of individual transducers disposed in a row in a generally horizontal plane, each transducer being capable of generating acoustical pressure waves in a generally upward direction,   an elongate reservoir for receiving a liquid coating material, said liquid coating material having an upper surface;   means for mounting each of said transducers in said reservoir such that said transducers are submerged beneath the surface of said liquid coating material, each of said transducers comprising a housing have an open top, a crystal element mounted in said housing for generating acoustical pressure waves upwardly, and a lens element mounted in said housing above said crystal element for focusing said acoustical pressure waves at a focal point in the vicinity of the upper surface of the liquid coating material, each of said mounting means being operative for permitting adjustment of a vertical elevation of said transducer, and adjustment of a rotational alignment of said transducer;   means for maintaining a constant liquid level of said liquid coating material in said reservoir;   means for selectively supplying electrical energy to each of said transducers, said energy being sufficient to cause said transducers to generate acoustical pressure waves and cause droplets of said coating material to be expelled form the surface of said coating material; and   means for advancing an object in a generally horizontal direction above said reservoir.   
     
     
       2. The apparatus of claim 1, wherein said means for mounting each of said transducers comprises an inwardly threaded opening in a bottom wall of said reservoir and an outwardly threaded cylindrical neck portion of said housing, said threaded neck being threadedly received in said threaded opening. 
     
     
       3. A transducer array comprising: a plurality of individual, independent transducers;   means for selectively supplying electrical energy to each of said transducers, said energy being sufficient to cause said transducers to generate acoustical pressure waves;   a reservoir for receiving a liquid coating material, said liquid coating material having an upper surface;   means for mounting each of said transducers in said reservoir such that said transducers are submerged beneath the surface of said liquid coating material and said acoustical pressure waves are directed toward the upper surface of said liquid coating material, said means for mounting being operative for permitting adjustment of a vertical elevation of said transducer, said means for mounting further permitting adjustment of a rotational position of said transducer relative to said reservoir; and   means for maintaining a constant liquid level of said liquid coating material in said reservoir.   
     
     
       4. The transducer array of claim 3 wherein each of said transducers comprises a housing having an open top, a crystal element mounted in said housing for generating acoustical pressure waves upwardly, and a lens element mounted in said housing above said crystal element for focusing said acoustical pressure waves. 
     
     
       5. The transducer array of claim 4 wherein said means for mounting comprises an inwardly threaded opening in a bottom wall of said reservoir and an outwardly threaded cylindrical neck portion of said housing of said transducer, said threaded neck being threadedly received in said threaded opening. 
     
     
       6. Apparatus for selectively coating a surface of an object with a coating material comprising: a plurality of individual, independent transducers;   means for selectively suppling electrical energy to each of said transducers;   a reservoir for receiving a liquid coating material, said liquid coating material having an upper surface;   means for mounting each of said transducers in said reservoir such that said transducers are submerged beneath the surface of said liquid coating material, said means for mounting being operative for permitting adjustment of a vertical elevation of said transducer so as to adjust a focal point of said acoustical pressure waves adjacent the upper surface of said liquid coating material whereby said acoustical pressure waves cause droplets of said coating material to be expelled from the surface of said coating material, said means for mounting being further operative for permitting adjustment of a rotational alignment of said transducer with respect to the reservoir;   means for maintaining a constant liquid level of said liquid coating material in said reservoir; and   means for advancing an object in a generally horizontal direction above said reservoir whereby said expelled droplets are received onto a downwardly facing surface of said object.   
     
     
       7. The selective coating apparatus of claim 6 wherein each of said transducers comprises a housing having an open top, a crystal element mounted in said housing for generating acoustical pressure waves upwardly, and a lens element mounted in said housing above said crystal element for focusing said acoustical pressure waves. 
     
     
       8. The selective coating apparatus of claim 7, wherein said means for mounting said transducer comprises an inwardly threaded opening in a bottom wall of said reservoir and an outwardly threaded cylindrical neck portion of said housing, said threaded neck being threadedly received in said threaded opening.